Toshiba Develops World's First Circuit Technology For 0.5V Operation of LSIs-- Power Consumption Cut to 1/100

8 February, 1996

Tokyo -- Toshiba Corporation today announced an innovative technology that will make possible LSIs with an operating voltage of only 0.5V. LSI operation at this low level will cut power consumption to 1/100 of that required for 5V LSIs and to 1/40 that for 3.3V LSIs.

Demand for lower power consumption level LSIs accompanies efforts to develop more powerful portable information and communications equipment with a longer operating life on a single battery charge. The relation between operating voltage and power consumption is geometric: a two-fold increase in operating voltage increases power consumption 4 times, a 4-fold increase by 16 times. By the same token, reduction in operating voltage significantly cuts power consumption. Toshiba's new LSI structure points the way to more powerful, power-efficient portable equipment operating at 0.5V.

The low operating voltage results from an innovative circuit structure and control methodology developed by researchers at Toshiba's ULSI Research Labs. The structure allows the threshold voltage -- the voltage level below which transistors switch off and above which they switch on -- to be individually controlled for each transistor in the LSI, and supports practical functioning of devices at 0.5V.

Current LSI design fixes a common threshold voltage for all transistors, at a level being determined by the characteristics of the substrate material. The major barrier to the much lower 0.5V LSI operation is achieving a threshold level below 0.5V that supports transistor switching while the error-causing leakage in charged voltage that occurs at such low voltage tolerances is avoided. Toshiba's newly developed circuit technology controls the threshold voltage of each transistor separately. This allows the threshold voltage of transistors in an on state to be kept at a lower voltage level, supporting high speed operation; when transistors are switched to an off state, the voltages is raised to a higher level, preventing charged voltage leakage.

Toshiba's new approach makes use of the fact that the threshold voltage of a transistor decreases when the electrostatic level of the substrate on which it is fabricated is high, and vice versa. The design uses silicon-on-insulator (SOI) substrate technology to isolate transistors from one another, and an original structure allowing individual control of the electrostatic level of each transistor's substrate as well as its threshold voltage. This assures that the threshold voltage is kept to under 0.2V when the transistor is on and at 0.5V when it is off.

Reduction of the operating voltage to these low levels was also contributed to by the adoption of mutual control of threshold voltage by the operating transistor and the next transistor to be switched.

Dr. Akimichi Hojo, General Manager of ULSI Research Labs, said: " Finding a practical way to lower the operating voltage of LSIs is a major concern. I believe our new technology is a major step forward, one with great potential for practical application."

The new technology will be officially announced at the International Solid State Circuits Conference, to be held in San Francisco from February 8th to 10th.

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